This invention relates to an apparatus and process for chopping continuous fibers into discrete fiber lengths. More specifically, the apparatus uses a unique combination of cutting blades and springs to chop the discrete fiber lengths.
Fiber choppers typically use cutting rollers to break continuous rovings into individual short fiber lengths. These choppers use a hard rubber back up roll as an anvil which cooperates with the cutting roller carrying one or more transversely extending blades. The back up roller and cutting roller cooperate to chop a discrete fiber length off the continuous roving each time a rotor blade contacts the back up roll.
The industry continues to develop new ways to cut filaments into staple fibers. One apparatus cuts the filaments with a cutting roller having circular cutting disks and disk shaped spacers. A fiber aligner aligns the segments in a transverse direction. A conventional chopper then cuts the segments a second time. Another apparatus uses axially parallel cutting blades held in receiving grooves with retainer strips. These cutting rollers work well for producing chopped fibers such as conventional chopped glass fibers.
Continuous filaments include a single filament or a plurality of filaments in a strand, with the filament having continuous length or substantial length, e.g., greater than one foot. A plurality of filaments is a plurality of segments of a single filament in adjacent relationships, such as occurs when a single filament is wrapped around a bobbin tube. Formation of the filaments also normally involves treating the filaments with a size to enhance the properties of the fiberglass in subsequent operations.
Recent advances, however, in after coatings for continuous filaments make the fibers more difficult to chop. The filaments are stiff and tuff and often have rubbery coatings. Conventional cutting rollers often don""t cut the stiff fibers. Results often leave the fibers bent or kinked. The typical result is not the clean cut industry desires. Further, the cutting rollers often break blades or do not penetrate the rubbery coatings.
I have developed a process and apparatus which overcomes the disadvantages of the previous cutting rollers for chopping continuous filaments. My apparatus for chopping continuous fibers into discrete fiber lengths includes a plurality of cutting blades mounted on a chopping roller. A spring holds the blades on the roller. The apparatus also includes at least one means for feeding at least one continuous fiber to the cutting roller. A feed roller is positioned parallel to the chopping roller. Preferably, the continuous fiber passes between the chopping roller and feed roller (for chopping the continuous fibers into discrete fiber lengths). The feed roller forms a nip with the cutting roller. Preferably, the spring is a spring washer. Preferably, the apparatus also includes an idler roller parallel to the feed roller. The idle roller forms a nip with the feed roller.
Preferably the feed roller has a hard cutting surface.